SNI will make it possible to support virtual SSL hosting on a single IP which would allow more websites to consider end-to-end SSL support
For Mozilla, there are thebugs filed for support of this

Guess which company the engineer works who has the bug assigned to him. You are right, It’s Sun Microsystems.

So here’s a shout-out to the Sun bloggers out there. If you believe that making it easier for webhosters (who may purchase Sun hardware if they find that SSL performance on the Sun Niagara boxes screams to easily host virtual SSL hosts on a single IP is a worthwhile proposition, then I encourage you to evangalize within the organisation to enable the engineering resources within Sun so that Mozilla/Firefox have support for SNI at the earliest.

Remember that a large percentage of the world isn’t going to move to Vista so SNI support in Firefox may even lead to a faster adoption of the browser and help in standard adoption